P is x% more than Q. Q is (x - 10)% less than R. If P > R, what is the range…

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P is x% more than Q. Q is (x - 10)% less than R. If P > R, what is the range of values x can take?

  1. A.

    10% to 28%

  2. B.

    10% to 25%

  3. C.

    10% to 37%

  4. D.

    10% to 43%

Attempted by 115 students.

Show answer & explanation

Correct answer: C

Given relations:

  • P is x% more than Q, so P = Q(1 + x/100).

  • Q is (x - 10)% less than R, so Q = R(1 - (x-10)/100) = R((110 - x)/100).

Express R in terms of Q:

R = Q / ((110 - x)/100) = 100Q/(110 - x).

Given P > R, substitute the expressions and cancel Q (assuming Q > 0):

(100 + x)/100 > 100/(110 - x).

Cross-multiply to remove denominators (valid if 110 - x > 0; we'll consider this):

(100 + x)(110 - x) > 10000.

Expand and rearrange:

  • 11000 + 10x - x^2 > 10000 → 1000 + 10x - x^2 > 0

  • Rewrite: x^2 - 10x - 1000 < 0.

Solve the quadratic equation x^2 - 10x - 1000 = 0 to find the boundary points:

Roots: x = [10 ± sqrt(100 + 4000)]/2 = [10 ± sqrt(4100)]/2 ≈ -27.02 and 37.02.

Because the quadratic opens upward, the inequality x^2 - 10x - 1000 < 0 holds between the roots:

-27.02 < x < 37.02.

Interpretation in the percentage context:

  • The phrase "Q is (x - 10)% less than R" implies x - 10 ≥ 0 (so that it is actually a reduction), hence x ≥ 10.

  • Combine this with the inequality: 10 ≤ x < 37.02.

Therefore, in percentage terms x can range from 10% up to about 37%. (So the correct choice giving 10% to 37% is justified.)

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